Abstract:In order to solve the problem that operation strategy of hydro-photovoltaic (PV) hybrid system is difficult to operate due to the uncontrollability and strong randomness of PV output, an intra-day optimal operation strategy with the index of fluctuating power ratio was proposed on the basis of influence analysis of PV output’s fluctuation characteristics on hydropower’s operation mode. First, an index system to describe both local and global characteristics of PV output was established, based on which the PV output scenarios were created by cluster analysis method. Then, considering both electric energy production and output fluctuation of the hybrid system, a new index named fluctuating power ratio was proposed, with which an optimized model was established. Third, combined with PV output characteristics, a particle swarm optimization (PSO) algorithm based on sigmoid function was proposed to solve the model. Finally, a case study was carried out for a series of small-scale hydropower stations developed in series and in parallel in a river basin in Sichuan Province. The results showed that the fluctuating power ratios in sunny, cloudy, and rainy days were within 0.05% after the complementary operation; compared with the optimization of hydropower alone, the access of PV improved the utilization rate of cascade reservoirs; and the proposed algorithm and model were proved to be feasible and scientific. It was demonstrated that the intra-day optimal operation strategy of hydropower in the hydro-PV hybrid system was as follows: The reservoirs discharged water to generate electricity while the PV output was small, then gradually stored water with the increased of the PV output, and started to discharge around the non-power generation period of PV until reaching the water stage at the end of the day.